Marine propeller



F. E. THOMPSON, JR 2,498,.34 I

Feb. 21, 1950 I MARINE FROPELLER 3 Sheets-Sheet 2 Filed May 29, 1947 FIG 13 INVENTOR.

FRANK E. THOMPSON JR.

flATTQRNEY Feb. 21, 1950 E. E. THOMPSON, JR

MARINE PROPELLER 3 Sheets-Sheet 3 Filed May 29, 1947 FIG. 10

INVENTOR. FRANK E. THOMPSON JR.

// ATTORNEY Patented Feb. 21, 1950 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to marine propellers and particularly to one with blades and hub of reinforced rubber.

It has long been an object of those engaged in the designing of marine propellers to develop one which will not foul in weeds. Heretofore, attempts to solve this problem have generally involved the use of guards to deflect the weeds before they reach the propeller. This has not proved satisfactory for several reasons, of which at least a major one is that in order not to prevent the efficient functioning of the propeller,

guards of this type must leave large openings for the free passage of water. When this is done, many weeds still get through to the propeller despite the guard. Further, these guards are expensive and by reason of their exposed position quite subject to damage. When used on an outboard motor they often add considerable weight, which is a serious factor, especially when the units have to be portaged to and from the place of use.

Another problem which has long troubled propeller designers is the damage resulting to propellers from striking submerged objects, such as logs. This likewise has in the past largely been met by the provision of some form of metallic guard.

By extensive experimentation I have found rubber to possess the unexpected and unique quality of being able, in the form of a propeller, to pass through Weeds Without such propellers becoming fouled by them. Experiments show that weeds will slip off a rubber propeller under conditions which would render the conventional metallic propeller useless. In addition to possessin this unique anti-fouling characteristic, rubber has the well known property of flexibility which renders it an ideal solution to the injury problem. By reason of this characteristic it will deflect upon striking a foreign object without sustaining injury.

Accordingly, a major object of my invention has been to provide a marine propeller which will pass freely through weeds without fouling.

A further object of the invention has been to provide a marine propeller which will not be readily injured upon striking submerged objects, such as rocks or logs.

A further object has been to develop a specific propeller construction by which the newly discovered non-fouling characteristic of rubber could be utilized.

A further object has been to provide a means of reinforcing a rubber propeller such that a balonce is provided between rigidity and flexibility at a point which will permit the unit to produce substantially the same thrust as a metallic propeller yet be capable of substantial deflection under conditions of excessive load.

A further object has been to provide a reinforcement construction for a rubber propeller which will both permit deflection of the blades and which will strengthen the rubber against tearing.

A further object has been to provide a means of securely gripping the rubber to the reinforcement and thereby preventing separation between the two.

Another object has been to provide a metallic hub core capable of giving ample support to the rubber hub casing in the direction of thrust.

Another object has been to provide a hub core and reinforcement of such a type that it will be cheap and quick to manufacture.

Other objects and purposes of my invention will be apparent to those acquainted with equipment of this sort and the problems which it is intended to solve, upon reference to the accompanying drawings and. the following specification.

In the drawings:

Figure 1 is a rear elevational view of my propeller.

Figure 2 is a sectional View of the hub of my propeller taken along the plane IIII of Figure 1.

Figure 3 is a right hand side elevational View of my propeller.

Figure 4 is a partial sectional view of the huband propeller blades taken along the plane IVIV of Figure 3.

Figure 5 is an enlarged fragmentary view showing only the end of the reinforcing support.

Figure 6 is an enlarged fragmentary rear elevational view of the reinforcing support taken along the plane VI--VI of Figure 5.

Figure 7 is a fragmentary rear elevational view showing a variation of my reinforcing.

Figure 8 is a detail of the attachment of the reinforcing shown in Figure '7 to the reinforcing support.

Figure 9 is a fragmentary rear elevational view showing an additional variation of my reinforcmg.

Figure 10 is a detail of the attachment of the reinforcing shown in Figure 9 to the reinforcing support.

Figure 11 is a detail of the reinforcing structure shown in Figure 9.

Figure 12 is a fragmentary View of the propeller shown in Figure 3 showing the entirety of the hub in front elevation.

Figure 13 is a fragmentary view taken along the plane XIIIXIII of Figure 1 showing the flexible reinforcement only, and a portion of the helical member.

Figure 14 is a fragmentary front elevational View taken along the plane XIV-XIV of ure 13.

In providing means meeting the objects and purposes outlined above, I have provided a structure which includes1a hub comprising a rubber shell mounted over a multi-step metallic core. This core has opposed laterally projecting rigid inserts, to the ends of which are attached flexible inserts. A heavy rubber shell integral .wiith the hub shell is molded over these reinforcements to form a complete smooth coating for the entire structure. For conveniencein description, the terms forward, rearward, left and right will be freely used in the following specification and will always be taken to mean in relati'on to the propeller as mounted on the aft of a boat and viewed'iacing the rear. Further, for the sake of simplicity, 'the description, except as otherwise "expressly appearing, will be given in terms o'f only one blade, it being unders'tood'th'atthe bladesof thepropeller are all'identic-al toeach other. A two-bladed propeller is here utilized for illustrative purposes, although the invention could as Well be expressed in other "multi bladed propellers or in a counter-weighted singlebladedpropeller.

Description Referring now -.to the drawings in more detail,

'the' numeral l indioates-a metallic hub core (Fig. i

2) with a central openingi suitable to accommofdate aconventional propeller drive shaft designed for use witha propeller of the dimensions involved. The thickness --of the core increases in a forward direction in'a-series-of annularsteps 3.

Thepurpose 'of thesesteps will be explained hereinafter.

On the forward end of the core there is a shear-pin key-way 4 extending radially outward in opposite directions from the'ce'n'tral opening '2 a distance equal to or more than half of 'the radius of the core (Fig. 12). This key-way and shear-pin associated therewith are conventional both as to location and as tosize andform 'no fti'on, where it exists, in the centerline of the blades. The rigid inserts are preferably substantially rectangular in cross-section and are provided with a slot-type end opening 'fi'parallel to the central placeof the end portion of the said insert. Two openings 1 (Figs. 5 and 6)y'are provided through each'of the walls 8 of'theslottype-openings suitable to accommodate rivets 'or similar fastening means (Figs. 5 and 6). The opening 6 is of sufficient depth to provide substantial edge margin for the fastening means in- "stalled in the openings '1! in a reinforcement, to be l'rer'einarf-ter idescribed,

between the walls 8.

inserted into the slot 7 in 'all "dimensions.

:inafter. usedbut those of approximate-13 inch diameter reproduce highly satisfactory results forthe usual When the propeller diameter is 4 inches or less the rigid reinforcements 5 may be omitted; however, excepting possibly only under conditions of exceptionally small thrust, a more satisfactory product is provided in even these small sizes when the rigid reinforcements are used. In sizes above 4 inches in diameter they are, in substantially all cases, essential to satisfactory performance.

A fie'xible blade reinforcement iinsert 9 extends outwardly fromthe insert?) (Figs. 1, 13 and 14).

.As shown in these figures, the body of the insert 9 comprises several layers I ll of heavy cloth bonde'ditogether by any suitable bonding agent, such as resin,glue or rubber.

'Thisflexible insert 9 corresponds substantially in shape to that portion of the blade extending beyond the rigid insert 5 but is materially smaller Sufiicient distance must remain between the perimeter of the flexible insert and the edge-of the blade '12 to permit-the rubber covering to be reduced to a thin ed'ge cross-section while maintaining a smooth and efiicient hydrodynamic curve. The thickness of this iflexible insert must likewise be sufiiciently limitedthat a rubber covering of 'su'ilicient-thicb ness 'toprovide necessary "strength may be provided without exceeding blade thickness limitations of good hydrodynamic blade design.

Openings H are provided through the cloth, especially in-propellers-of overl'0inch diameters. These serve'as a means (if-anchoring the molded rubbershellas will be explained more fully here- A wide latitude of "hole sizes may be six to ten in'ch blad'es.

The periphery of the ilex'ible insert is pierced with a series of small diameter openings 1 3. -A resilient, preferably :m'etallic, helical coil 1'4 is passed through these openings, each hole accommodating one loop. As a variation, an in- 'dividual rnetalli'c"ring in each *hole may be sub- -tac'hin g "holes 13, together with "the openings 1 I,

may be eliminated and the propeller unit will maintain a workable, though perhaps 'less satisfactory, balance between rigidity-"and flexibility.

Two or 'more'installation openings #5, suitable for rivets or similar-fastening means, are ;pro-

vided through the flexible "insert "9 proximate to the edge nearest the bent-ralaxis ofthepropeller.

These openings are coordinated with the *openings "lthroughthe end of'th'e rigid insert 5.

The clothfiexible insert 9 "together with the coil 1'4 may be replaced with a fan-type .ar-

rangement 23 of single ormultiple strand "wires (Fig.7). A mountingbase I56 isj'provided-(Fi 8.) which may consist "of metal or a strong, rigid plastic and havin'g'twoormore'instailation openings 1], suitable "for rivets-"0r similar fastening means, through the *mounting base and coordinated'with the openings '1 'in'therigid insert 5. A multiplicity of individual metallic wirespokes ii; are inserted inthe base. Eachofthese wires are of 'difierent lengths and are given suitable degrees of deflection to-c'oordinate-wit'h the 'central plane of the blade. The two end-wires i9 and 20 are givezrthe greatest-degreeof -deflection. The ireeendsdf these wires, are joined and formed substantially to parallel the perimeter l2 of the blade. The spoke wires and the capping wire are attached by soldering, welding or wrapping. One or more bracing wires 22, depending upon the diameter of the propeller, may be used at suitable spacing or spacings between the mounting base IB and the capping wire 2|. The bracing wire 22 may be attached to the spoke wires in a manner similar to the joining wire 2!. The overall size of the fantype flexible insert 23 is substantially similar to the size of the cloth insert 9 for propellers of corresponding diameters.

A further variation in the type of flexible insert may be made by the use of a wire cloth 24 consisting of interlocking individual metallic wire rings 25 (Figs. 9, 10 and 11). This is cut to form flexible reinforcement body substantially similar in size and shape to the cloth insert 9.

Assembly To assemble a propeller of the type illustrated in Figures 1, 2, 13 and 14, the flexible inserts 9 are attached to the rigid inserts 5 of the core. This is accomplished by inserting the flexible insert 9 into the slot-type opening 6 (Figure 5) until the openings 1 and I5 are in register. Rivets 26, or other suitable fastenings means, are then passed through the holes and locked into position in any usual manner (Fig. 1). By means the rigid and the flexible reinforcements are securely locked together as a single unit.

The flexible, fan-type insert 23 is secured to the rigid inserts 5 by its mounting base H5 in the same manner as the flexible cloth insert 9 (Figs. 7 and 8) The rivets 29 perform the same function and may be installed in the same manner as the rivets 26.

The flexible wire cloth insert 24 is mounted to the rigid insert 5 by passing a portion of the insert into the slot-type openings 6 (Figs. 9, 10 and 11). The links 25 within the opening are then soldered to the walls 8 as indicated at 30. Rivets 3! may then be installed as an additional fastening means if desired.

When the inserts have been assembled and fastened together a rubber body or housing 32 is then molded over the entire unit to form a complete shell about the inserts. Any good grade of natural or synthetic rubber of a Shore hardness between and H30, preferably for most uses between 60 and 80, may be used for this shell, excepting only that it should have a fair degree of flexibility and tensile strength. A rubber of low tensile strength and low flexibility, such as reclaimed rubber, will not be particularly satisfactory. The exterior surface 33 of the hub portion of this shell 32 is substantially in the form of a truncated hyperbola (Fig. 2). The rubber is molded tightly into the steps 3 for reasons which will appear more fully hereinafter. The rubber shell 32 is molded at the forward end to provide two circular depressions 34 and 35 (Fig. 2) to clear the structure to which the propeller is attached (not shown as it forms no part of this invention).

The rubber shell 35 of the propeller blades is molded integral with the rubber shell 32 of the hub. The exterior shape of this shell is that conventional for marine propellers, except that suflicient thickness must be provided to contain the inserts, and conforms to the accepted principles of hydrodynamic design. Since this form is conventional and forms no part of my invention, further description of it will not be iven.

As the rubber shell 36 of the blades is molded about the flexible insert 9, a portion of the rubher will pass through the openings II to form posts 31 of rubber through the flexible inserts (Fig. 1). The rubber will also fill in the interstices between the wires of the coil I l. The area between the flexible and rigid inserts and the edge of the blades I2 is filled entirely by the rubber shell 36.

The rubber will in a similar manner fill the spaces and interstices existing within the members of the flexible inserts 23 and. 2 (Figs. '7 and 9).

Since the propeller, to be practical, must develop sufficient rigidity to provide thrust while at the same time have enough flexibility that it will deflect under any excessive load such as striking a submerged rock or becoming fouled with weeds, the rubber should be of maximum softness, i. e. flexibility consistent with having the capacity to transmit the desired torque. Thus, an outboard motor propeller for trolling will be of relatively high flexibility while an inboard motor propeller for general use will be of relatively less flexibility. In addition to selecting rubber of proper flexibility, it will be understood that the flexibility of the blade may also be controlled by proper designing of both of the inserts as to size and shape and selection of material to provide flexible inserts of the desired size and stiffness.

Operation The hub core I provides a rigid, wear resisting means of transmitting torque from the driving shaft (not illustrated), passing through the central opening 2 thereof, to the remainder of the propeller unit.

Whenv the rubber is molded about the hub core i it bonds thereto to form a single operational unit. As the propeller is rotated, it develops thrust on its parts in the direction of the arrow (Fig. 2). That portion Of the thrust load carried by the rubber shell 32 is transmitted to the hub core I by means of the steps 3. The vertical faces 38 of these steps provide direct support for the rubber shell at right angles to the direction of the thrust load and relieve the shell of its load in evenly distributed proportions.

The major portion of the thrust load is transmitted from the blades to the core by the inserts 5. Besides transmitting the thrust load, the rigid inserts provide support for the rubber shell 36 of the blades. Inasmuch as rubber Without support is both too flexible and too low in ultimate tensile strength to provide a. satisfactory propeller over four inches in diameter, these rigid inserts are necessary to overcome this difliculty. The flexible inserts 9, 23 or 2 pick up the load created by the extended portions of the blades and transmit it to the rigid inserts 5. They supplement and overcome the absence of tensile strength in the unsupported rubber without materially affecting its flexibility characteristics. They are designed to permit, when necessary, a large portion of the blade to deflect without tearing. The openings II in the insert 9 and the numerous interstices created by the coil H1, or the spaces between the wires in Figure I, or between the rings 25 in Figure 9, provide a large number of individual anchorages for the rubber shell assuring a firm bond between the shell and the inserts.

c ass ess 'ltrwillbe understood thatsmanyrother types-30f flexible inserts, and insert material, such as high grade kraftrgpaper, lor =wood 'or-themp :fibers, may beiusedsimaddition to ithat herein specifically illustrated, providedionlyit is:properly:flexible and will apermitmubber tOZbOl'ld Ltoitaeitherbytchemicalzaction clirectly'toaa smooth-surface'or by enter- .ingzsuit'ableinterstices.

.Aslin the 'case of the hubuasufiicientspace is :provided betweenrthe inserts :and the edge of :the blade l2 to assure tapering the thickness 10f the "blade Etowardsrtheaedge "while maintaining efficienthydrodynamie characteristics.

Therubbershells 32 and 36.:providea smooth, all rubber surface for the propeller which ,w'illnot ioulliniweeds'since the weeds will lfreely slide ofi. Thesentirety of therblades has: sufiicient'stifiness to transmit the torque :ior which the propeller is :designed but it'will besufficiently flexible-to; avoid iinjury tOfltSGlfillIlOl'i striking obstructionssuchas :submerged logs :or'zrocks.

Several other'variationsrma-ybe made irom'the specific structures herein disclosed, especially. in size and stiffness characteristics, 'Without departure from the principles ofmy "invention and Zhence the (hereinafter appended 'claims should be interpreted ltozcover such variations excepting where the claims by their own terms expressly zprovidez'otherwise.

1. :Acomposite axial fiow marine propellercom- 'zprising :in combination: :a metallic hub core with an exterior surface divided into lcircumferential steps of radius progressively increasing in one direction along the axis orsaid hub core; a plurality of rigid inserts integral withsaid -hub core and projecting radially therefrom; .a flexible insert composed of aplurality .oflayers of cloth bonded togetherlmounted upon and projecting radially from the ends of each of said rigid inserts; a resilient -coil along the periphery of said flexible insert; a rubber shell having a smoothlhydrodynamically shaped exteriorsurface surrounding saidhub coreand'bonded thereto; ablade-shaped rubber shell surrounding each of said combinatime nfra rigid insertand a :fiexible insert and J prising in combination: a metallic hub core; a plurality ofwrigidinserts aifixed-tosaid hub Score and projecting radially therefrom; a flexible insert mounted upon'andprojecting radially from the ends of .eachnof .said rigid inserts; a resilient coil along therperiphery of .said flexible insert; a rubber shell 'havingla smooth, hydrodynamically shaped exterior surface surrounding said hub core andlboncled-thereto; a blade-shaped rubber shell surrounding each of saidcombinations of arigid 2111116 .affiexible insert and integral with said hub ell.

FRANK E. THOMPSON, JR.

REFERENCES CITED The following references :are'of record in the file of this patent:

UNITED sTATEs PATENTS Number 7 Name Date 1";3981'52'7 Nilson July 1, '1919 1,384,308 De Giers .July. 12, 1921 134191061 Kraft June 6,1922 134191 Thomson June "13, 1922 2,077,959 Smith .Apr.120, 1937 2,183,891 Newn'h'am Dec. 19, 1939 "2,251,887 Larsh Aug. 5, 1941 2,4731665 'Van'Nort June 21, I949 

